Thin film deposition for semiconductor device fabrication is generally carried out through a gas phase process, such as chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD) or atomic layer deposition (ALD). In such a process a liquid chemical precursor is generally vaporized with the help of a carrier gas to form a vapor/gas mixture. The mixture then flows into a deposition chamber for thin film deposition on a substrate. The deposition chamber is usually maintained at a vacuum in order to meet the desired process conditions.
Following deposition, the gas/vapor mixture then flows through a vacuum pump for exhaust to the ambient atmosphere. During its passage through the pump, the vapor, which is chemically reactive, can react with the pump oil to change the physical and/or chemical characteristics of the oil. Over time, the pump oil becomes contaminated with the reactive precursor vapor and is no longer capable of maintaining the deposition chamber at the desired vacuum pressure. When this occurs, the system must be shut down for pump maintenance, leading to the loss of productivity for the deposition system.
To reduce the frequency of pump maintenance, various exhaust treatment devices have been developed and used in the semiconductor industry. They range from devices that use high temperature plasma to decompose the precursor vapor to systems that inject vapor to react with the precursor vapor to render them less harmful. While these measures can prolong or extend the operating life of the pump, they do not provide a permanent solution for the problem.